The present invention concerns a method for the Production of an intermediate product, which can be inject-on moulded, from a dry, pasty or fluid raw material and at least one binding agent.
Known in the art is the production of intermediate products, which can be injection moulded, by kneading of raw materials together with a binding agent in a device.
In the conventional methods, the raw materials are processed together with the binding agent within the device (kneading device) with the assistance of knead elements, warmed by a separate heating device and kneaded into a paste after melting of the binding agent. The paste can then be removed from the device, and the extracted intermediate product, designated as "feedstock" (paste), can be injection moulded into a product to be produced. This object must still be subjected to baking or sintering processing for curing and is referred to as a "green body". The intermediate product must optionally be further processed prior to injection moulding. This further processing can consist essentially of a granulation or a grinding of the cooled paste.
In order to manufacture the intermediate product, it is necessary for the raw materials and the binding agent to disadvantageously be kneaded for 2 to 20 hours.
Due to the low mixing effectivity of the kneading device, the produced paste has a limited degree of homogeneity. This low or absent homogeneity affects the recycling process or the utilization of the waste products occurring from injection moulding which are once more introduced into the device. It has turned out that there is a strong difference in flow properties between the pure raw materials and the recycled product wastes. The inadequate homogeneity of the paste also leads to the need for post-processing the paste optionally in an extruder or in a cylinder mill.
The kneading processing of a mixture comprising raw materials and at least one binding agent is only possible in dependence on the mixture utilized by selecting an appropriate mixture. Not all types of kneading devices are suitable for each mixture so that, under certain circumstances, the mixture must be changed.
It is the purpose of the present invention to develop a method for as effective production as possible of a high quality intermediate product which can be injection moulded.